1. Field of Invention
This invention relates to a method of producing precast concrete panels with built-in outer frames of sash windows or the like.
2. Prior Art
In the factory precasting of concrete wall panels integral with the outer frames of sash windows or the like, the usual practice has been to install the outer sash frame on the bottom of a form into which concrete is to be cast and to place a holder frame over the outer sash frame. The outer sash frame is then secured in position as by bolting. This conventional practice has a disadvantage in connection with a highly involved procedure required for the installation of the outer sash frame and for the assembly and disassembly of the form.
It has also been the practice heretofore to secure the entire outer sash frame, or at least the corners thereof, to the form. This practice is objectionable because the outer sash frame is restrained from elongation or expansion in the steam curing of the concrete cast in the form. The outer sash frame that has been built into the concrete panel in this manner tends to buckle out in its mid-portions. When the sashes are installed in the outer frame, therefore, unnecessary gaps may exist between the sashes and outer frame, or the sashes may not be smoothly movable between their closed and open positions.